One other thing.
When the shows were made (mid 70s) there were far fewer ethnic people in this country.
People from other ethnic groups were considered somewhat "strange" and "different" and it is true to say that as a nation we were FAR more racist than we are now.
The black and white minstrels show (white men "blacked up") was shown on TV right up to 1978 with barely a complaint (even Lennie Henry appeared on it)
http://www.sterlingtimes.org/memorable_images2 9.htm
Golliw0gs were used to advertise jam and sold in toy shops like teddy bears are today.
If a black or asian actor was required in a TV show or film often a white person was used to play the part, Spike Milligan appeared as an Asian on TV, as did Peter Sellers in some films.
I remember a scene in an Only Fools and Horses where uncle Albert comes in with some shopping and says "I have just been to the pak1 shop". And that was not that long ago.
I remember a scene in Till Death do us part where Alf said he would refuse to accept a black persons blood if he needed a blood transfusion (although to be fair the show was written to point out that Alf was racist).
It was a diffferent world then, and it is hard to imagine any of the things I have listed above happening today.
So to sum up, you cannot judge what Rigsby says and does based on today's standards, only on the standards from the 1970s.